Frequently updated resource link with some commentary on the various offerings of web cams.

http://www.mac-compatible-web-cam.com/

Wikepedia article about UVC standards.  This is the standard that most if not all new web cams and many USB devices are adopting as it allows for pretty much true cross-platform compatibility.

http://en.wikipedia.org/wiki/USB_video_device_class

——————————————————————–

Here a few samples of UVC compliant Web Cams that should work natively with Tiger and Leopard: